Sri Ponnambalam Vaneswaram Temple is one of Colombo's most atmospheric Hindu temples, built in grey stone with carved pillars, shrines, and a notably calm interior. It feels quite different from the city's louder commercial streets and from the better-known Buddhist sights.
The temple is active, so the visit depends on timing, dress, and respectful behaviour. Go for the craftsmanship and the sense of devotion rather than for spectacle, and leave shoes and photography expectations at the door unless permission is clear.